This invention relates to an installation for the production of cement clinker from raw meal, which is preheated in at least two mutually parallel cyclone suspension heat exchanger trains and precalcined in a fueled calcination stage, from which the gas-solid suspension is fed by suspension splitting into the lowermost cyclone stage of each cyclone suspension heat exchanger train for the purpose of separating the precalcined raw meal from the off-gas stream, the precalcined raw meal substreams of all heat exchanger trains subsequently being fed into a rotary kiln for cement clinker burning.
Given that required production capacities are large, installations for the production of cement clinker from raw meal are often made as dual-train installations or twin systems having two separate, mutually parallel, fueled rotary kiln off-gas risers made as raw meal calciners and having two mutually parallel cyclone suspension heat exchanger trains through which the calciner off-gases flow, one raw meal substream being thermally treated in each of the two trains. Such an installation is disclosed in a KHD Humboldt Wedag AG brochure xe2x80x9cPYROCLONxe2x80x9d 7-222 d, 1979, pages 4 and 5, FIG. 3. It can happen that the gas and meal burdens of the gas-solid suspension differ from one calcination train to the other and from one heat exchanger train to the other, not least of all because of the sense of rotation of the rotary kiln to whose charging chamber the two trains are connected.
Also known are so-called hybrid installations in which the two above-described separate calciner trains are combined into a single calciner in shaft form, supplied with calcination fuel, through which rotary kiln off-gas flows, at the upper end of which calciner the upwardly flowing gas-solid suspension is split into two substreams, which are then led to the two heat exchanger trains via two pipe bends inclined away from each other. Such an installation is disclosed in Duda Cement Data Book, 2nd Edition, 1977, p. 419. Here again, it can happen that when the gas-solid suspension from the calciner is branched, the meal and gas contents in the several heat exchanger trains may differ, so that also the loadings of the several heat exchanger trains differ sharply, which has a detrimental effect on the specific heat requirement for the installation as a whole.
This problem is further aggravated if fuel fed at least one DeNOx unit in the rotary kiln off-gas riser, that is, in the calciner, is combusted under richer than stoichiometric conditions, that is, with an oxygen deficiency, in order to create a CO-containing reduction zone or CO gas strand for the reduction of the pollutant NOx formed, in particular, by high-temperature combustion in the rotary kiln (thermal NOx). The CO gas strand is then not uniformly distributed over the calciner cross section. Especially when the CO not consumed in the NOx reduction zone of the rotary kiln off-gas duct and the solid fuel particles initially not combusted in the calciner cannot be completely burned out, it can happen that unequal and also transient strand-wise fuel loadings may come about in the two heat exchanger trains.
It is therefore an object of the invention to create, for the production of cement clinker from raw meal, a two-train or multi-train installation such that it is guaranteed that the several cyclone suspension heat exchanger trains are no longer loaded with unequal gas and meal loads of the flowing gas-solid suspension.
The cement clinker production installation according to the invention, having heat exchanger lines made in dual-train or multi-train form and charged with a calcination off-gas suspension from a common calciner, is characterized in that a vortex chamber/mixing chamber/homogenization chamber, having an inlet opening for the gas-solid suspension and having at least two outlets for the exit of the thoroughly blended gas-solid suspension substreams, is arranged in the calcination stage, at latest at its end upstream of its branching and splitting between the several heat exchanger trains. In this homogenization chamber, the gas-solid suspension of the calciner is effectively thoroughly blended with a gas in a homogeneously loaded manner, for example, by CO strands before the thoroughly blended homogenized gas-solid suspension is subsequently split between the several heat exchanger trains, so that the specific heat requirement of the multi-train installation is minimized and its operational reliability is enhanced. This holds true especially for multi-train installations having DeNOx units in the calciner for DeNOx reduction in the off-gas, because the homogenization chamber also provides for intensive mixing of residual fuel constituents still present in the calciner as well as residual CO gas strands, etc., with atmospheric oxygen and thus provides for residual burnout and thus also a high degree of raw meal calcination (e.g., 95%).
The vortex chamber/mixing chamber/homogenization chamber with subsequent branching of the homogenized gas-solid suspension is made in such a fashion that it equalizes in homogeneities of the inflowing gas-solid suspension by intensive mixing. For this purpose, the inlet opening of the vortex chamber can be arranged such that a rotational component is superposed on the entering gas-solid suspension. It is, however, also possible that for this purpose a fixed or rotating swirl generator is built into the vortex chamber, for example on the cover of a vortex and separation can occur when the gas-solid suspension impinges centrally from beneath, the flow being deflected to the periphery, reversed downward and led to at least two bottom outlets for the homogenized gas-solid suspension for the purpose of splitting between the separate cyclone suspension heat exchanger trains.
For effective homogenization of the gas-solid suspension, the vortex chamber arranged in the calcination stage can have in its upper region an opening for the tangential inlet of the gas-solid suspension and at its bottom two or a plurality of outlets for the discharge of the mixed homogenized gas-solid suspension, these outlets each being connected via a pipeline to the lowermost cyclone stage of one of the cyclone suspension heat exchanger trains.